The present invention relates to a technique for a monitoring system for providing safety driving environment by displaying a processed image of the sate around a vehicle taken by a camera installed on the vehicle.
As an apparatus for monitoring the state around a vehicle by using a camera, a system in which an image taken by a camera installed on a rear trunk room or the like of a vehicle is presented to a driver is conventionally known. Thus, the driver can be informed of the state in the rear of the vehicle. Furthermore, a system for supporting a parking operation in which not only a camera image but also possible travel loci of tires overlapping the camera image are present has recently been known. Thus, the driver can grasp the state ahead in a moving direction of the vehicle.
A conventional system will be described with reference to FIGS. 8A through 8C. FIG. 8A is a schematic diagram of a camera installation mode, FIG. 8B shows an exemplified camera image obtained in the camera installation mode of FIG. 8A, and FIG. 8C shows an image obtained when the vehicle is moved straight backward by 25 cm from the position where the image of FIG. 8B is obtained. In the image of FIG. 8B, another vehicle parks just behind the vehicle, a dashed line A extending in the center indicates how the center of the vehicle behind approaches on the screen while the vehicle is moving straight backward, and solid lines B1 and B2 on the left and right hand sides indicate how the left and right corners of the vehicle behind approach on the screen while the vehicle is moving straight backward.
In the example shown in FIGS. 8A through 8C, when the vehicle is moved straight backward, an object present just behind the vehicle (i.e., another vehicle in this case) gets close to the vehicle in the downward direction vertically on the screen. Therefore, it can be easily grasped whether or not the center of the vehicle corresponds to the center of the object.
If the camera is installed so as to face to substantially the same direction as the straight reversing direction of the vehicle and to be positioned substantially at the center of the rear portion of the vehicle in the aforementioned conventional monitoring system, the system is very useful for a user. This is because an object moving vertically on the screen can be identified as an object present on an extended center line of the vehicle, and hence, the moving direction of the vehicle can be grasped intuitively on the basis of the displayed image.
However, if the camera is not installed at substantially the center of the rear portion of the vehicle, this conventional system has a problem.
For example, a license plate, a rear windshield wiper, a locking mechanism for a trunk room, a spare tire and the like are generally placed around the center of the rear portion of a vehicle, and hence it may be difficult to secure a place for installing the camera. Also, the position of the camera may be shifted so that a specified direction or region can be easily taken. For example, the position of the camera may be shifted toward the passenger's seat side so that a larger region on the passenger's seat side where a driver is difficult to see from the driver's seat can be taken.
In another camera installation mode shown in FIG. 2, the camera faces to the straight backward direction but its position is laterally shifted by approximately 50 cm from the center of the rear portion of the vehicle. FIG. 9A shows an exemplified camera image obtained in the camera installation mode of FIG. 2, and FIG. 9B shows an image obtained when the vehicle is moved straight backward by approximately 25 cm from the position where the image of FIG. 9A is taken. Also in FIG. 9A, the dashed line A and the solid lines B1 and B2 have the same meanings as in FIG. 8B.
In this case, another vehicle present just behind the vehicle is imaged in an area close to the edge of the screen, and hence, it is difficult to grasp, on the screen, the positional relationship between the vehicle and the other vehicle behind. Also, when the vehicle is moved straight backward, the other vehicle behind approaches not in the vertical direction but in an oblique direction on the screen.
In still another camera installation mode shown in FIG. 6, the camera faces to a direction slightly toward the center line rather than the straight backward direction and its position is laterally shifted by approximately 50 cm from the center of the rear portion of the vehicle. FIG. 10A shows an exemplified camera image taken in the cameral installation mode of FIG. 6, and FIG. 10B shows an image obtained when the vehicle is moved straight backward by approximately 25 cm from the position where the image of FIG. 10A is taken. Also in FIG. 10A, the dashed line A and the solid lines B1 and B2 have the same meanings as in FIGS. 8B and 9A.
In the case where the position of the camera is shifted from the rear center of the vehicle, if the camera faces to the straight backward direction of the vehicle as in FIG. 2, the visual range in a side rear region of the vehicle opposite to the camera installation position is small as is understood from FIG. 9A. In order to obtain a well-balanced image on the right and left sides of the vehicle, the camera should face to a direction toward the center line of the vehicle. When the images of FIGS. 10A and 9A are compared, it is understood that a left rear region of the vehicle is shown more largely in FIG. 10A.
In this case, when the vehicle is moved straight backward, another vehicle present just behind the vehicle approaches in a more oblique direction on the screen than in FIG. 9A.
In this manner, in the conventional system an object actually present just behind a vehicle is imaged in an area close to the edge of the screen or moves in an oblique direction on the screen when the vehicle is moved straight backward. Therefore, when such an image is presented to a user, the user may have an odd feeling to see the image, which makes it difficult to check whether or not the vehicle is moving straight backward or whether or not the center of the vehicle corresponds to that of a target. As a result, there is a fear of a driving operation error.